b 
514 Transactions. 
of the water. The thalli of Durvillea antarctica on exposed coasts assume 
the form of long narrow segments of nearly even width throughout. In 
more sheltered situations the thallus is broadly and irregularly palmate. 
wn 
In the size of the “leaves” of Carpophyllum an interesting comparison 
may be made between C. maschalocarpum, whic ows in fairly exposed 
placed and has small thick leaves, and C. phyllanthus, which affects harbours 
and sheltered inlets and is a very luxuriant form with large thin leaves. 
Macrocystis pyrifera, which possesses the largest and most easily torn leaves 
of the brown algae, occurs chiefly inside harbours, especially in tidal streams, 
and in deep water outside the break of the surf. 
The ribbon-like leaves of Zostera and Ruppia need only be mentioned 
here. These plants live in stations subject to tidal currents, but not to 
much wave-action. The action of waves is irregular and discontinuous, 
whereas that of currents is regular and constant, and this is reflected in 
the difference between branched and unbranched stems. Mr. W. A. Scarfe 
informs me that the ribbon-like form of Durvillea antarctica only occurs in 
places where current is added to wave-action. 
(5.) Hooked Claws.—Certain crustacea living on algae exposed to the 
surf are provided with sharp claws, which enable them to retain their 
positions while the seaweed is being bufleted about by the waves. Their 
use is in every respect similar to that of the hooks possessed by various 
crustacea living on fishes and cetaceans. Species of Idotea occur on various 
algae in the surf belt; their legs all terminate in hooked claws. Amphoroidea 
falcifer is found on Durvillea antarctica, and by its depressed form and | 
strong hooks is admirably adapted to its station. 
ORGANIC ENVIRONMENT. 
pointed out in a previous paragraph, these are also of service in the littoral ` 
belt for conserving moisture. Hermit-crabs, which have the hinder portion 
of the body quite unprotected, make use of empty gasteropod shells. 
(2.) Weapons.—Closely associated with armour are weapons of defence 
and attack. The chelae of crabs may be first mentioned. Powerful jaws 
are possessed by many polychaet worms; gasteropods employ their radulae 
for boring through the shells of their prey. The spines of echinoids and 
the stinging-cells of sea-anemones are effective weapons. 
(3.) Distasteful properties are possessed by many animals and plants 
The common sponges are quite unpalatable, owing to the presence of 
enemies, whilst the bright colour of many of the species perhaps serves 89 
LI . or bd 
) Assimilative Colouring —Instances of patterns of colouring resembling 
the surroundings, be it rock or algae, among which the animals live atè 
frequent in the littoral belt, and are presumed to be mainly for protective 
purposes. Fishes of the families Blennidae and Gobiesocidae are of various 
shades of black, grey, and pink with a mottled pattern. Nudibranchs and 
